It is common practice in the manufacture of mineral fiber insulation to pass the insulation between a pair of foraminous conveyors, or belts, mounted for travel through the curing oven. Hot gases are passed through the insulation to more effectively cure the binder in the insulation. Associated with the oven are supplies of hot curing gases, usually air, which travel generally upwardly or downwardly through the insulation. Typically, the curing ovens are divided into zones, and flexible seals are sometimes employed to prevent the passage of curing gases from one zone to an adjacent zone. A common construction for the belts is that of foraminous flights connected in series and driven by a chain. The ends of the flights are mounted on wheels which ride in tracks running the length of the oven.
One of the problems associated with ovens for curing mineral fibers is that the support means for the belts, which can include the wheels and the chains, are subjected to a hostile environment due to the high temperature of the hot curing gases. Typically, the gases reach temperatures as high as 500.degree. F. The moving parts in the form of wheel bearings and flexible chain linkages for pulling the flights through the oven require lubrication, and the lubricants themselves often react adversely in the hot oven environment. The heat of the curing gases can cause the lubricant to dry up, resulting in friction wear of the moving parts. Also, some of the lubricants oxidize, creating smoke which can become a source of air pollution.
Heretofore, the only means for preventing lubricant burn off and subsequent smoke generation and premature equipment wear, was to use costly specialty lubricants able to withstand the hot environment of a curing oven. The use of such high temperature lubricants has been only marginally satisfactory in performance, and has resulted in a greater operating expense in the manufacturing process.
Another problem associated with mineral fiber curing ovens is that although the general flow of curing gases through the oven is in the vertical direction, through the insulation material, it is believed that a substantial portion of the curing gases are flowing around the edges of the material and the belts, rather than through the material. For example, it is believed that a pressure drop from the top of the oven to the bottom equivalent to about 15 inches of water results in a pressure drop across the insulation material of only 2 to 3 inches of water. Thus, considerable inefficiencies can be involved with existing curing processes since much of the heated curing air is by-passing the product which is to be cured.
There has now been developed apparatus for curing fibrous mineral insulation material which overcomes the problems of existing ovens by providing baffles within the ovens to define a curing gas flow path which is through the belts and the insulation material, but which flow path is spaced apart from the wheels and the drive chain which support and move the belts through the oven. By employing the apparatus of the invention the chain and support mechanism including the wheels can be lubricated with a less costly and more reliable lubricant. A reduction in the burning off of the lubricant can substantially reduce the downtime required to fix the chains and other apparatus damaged by friction. Also, the apparatus of the present invention ensures that any smoke which is generated during the curing process is kept within the flow path, rather than being allowed to circulate throughout the curing oven, and potentially leaking out from the oven into the plant space.